The main factors affecting the cracking of seamless steel pipes
1) Defects of the original material: including the elemental composition segregation of the tube blank and non-metallic inclusions in the tube blank
2) The effect of metallographic structure on the cracking of seamless steel pipes
Precaution
1. Precautions against defects in original materials
1) Precautions against segregation of billet components.
Element segregation, that is, the phenomenon of uneven distribution of various gold elements in the tube blank during the crystallization process. The segregation of elements in the actual production process is generally the segregation of carbon content, because the carbon content of steel is usually the highest, and the segregation of carbon content can only be controlled or reduced by technical means, and cannot be completely avoided. The usual method is to control the cooling rate, the casting rate, and strengthen the stirring.
2) Preventive measures for non-metallic inclusions in tube blanks.
In general, the inclusions in the metal make the internal structure of the metal less uniform and reduce the internal continuity of the metal. In the production process of seamless steel pipes, there are two main sources of metal inclusions: internal and external factors.When there are internal inclusions, attention should be paid to increasing the use and content of deoxidizers in the steelmaking process, and nitrogen blowing can also be selected to reduce the presence of metal inclusions. For external reasons, some high-quality mold powder or high-quality refractory materials should be used, so as to reduce or even avoid steel-making mold powder being involved in molten steel.
2 Metallographic structure defect prevention measures
1) Band tissue precautions.
In the production process of seamless steel pipes, there are two main reasons for the formation of banded structures. One is that the temperature control of heating in the production process is not appropriate.In general, the band-like structure caused by deformation processing can be eliminated by heat treatment. The other is the band-like structure caused by the segregation of chemical components, which can usually be controlled by controlling the segregation of elements in the production process of steel pipes.
2) Preventive measures for abnormal metallographic structure
In the production process, some unexpected organizational components or organizational forms sometimes appear, which will cause abnormal metallographic structure, such as excessively coarse grains, uneven metal structure, and abnormal internal structure of the metal.The occurrence of the above situations is related to the on-site heat treatment process.If the steel pipe is in the heat treatment process, the improper control of the heat treatment temperature or conditions will make the metallographic phase of the metal structure abnormal. In the usual production process, the heat treatment of steel pipes is controlled according to the long-term accumulated experience. Controlling the corresponding temperature, holding time and cooling method during the heat treatment process can avoid metallographic abnormalities in the metal structure.
1) Defects of the original material: including the elemental composition segregation of the tube blank and non-metallic inclusions in the tube blank
2) The effect of metallographic structure on the cracking of seamless steel pipes
Precaution
1. Precautions against defects in original materials
1) Precautions against segregation of billet components.
Element segregation, that is, the phenomenon of uneven distribution of various gold elements in the tube blank during the crystallization process. The segregation of elements in the actual production process is generally the segregation of carbon content, because the carbon content of steel is usually the highest, and the segregation of carbon content can only be controlled or reduced by technical means, and cannot be completely avoided. The usual method is to control the cooling rate, the casting rate, and strengthen the stirring.
2) Preventive measures for non-metallic inclusions in tube blanks.
In general, the inclusions in the metal make the internal structure of the metal less uniform and reduce the internal continuity of the metal. In the production process of seamless steel pipes, there are two main sources of metal inclusions: internal and external factors.When there are internal inclusions, attention should be paid to increasing the use and content of deoxidizers in the steelmaking process, and nitrogen blowing can also be selected to reduce the presence of metal inclusions. For external reasons, some high-quality mold powder or high-quality refractory materials should be used, so as to reduce or even avoid steel-making mold powder being involved in molten steel.
2 Metallographic structure defect prevention measures
1) Band tissue precautions.
In the production process of seamless steel pipes, there are two main reasons for the formation of banded structures. One is that the temperature control of heating in the production process is not appropriate.In general, the band-like structure caused by deformation processing can be eliminated by heat treatment. The other is the band-like structure caused by the segregation of chemical components, which can usually be controlled by controlling the segregation of elements in the production process of steel pipes.
2) Preventive measures for abnormal metallographic structure
In the production process, some unexpected organizational components or organizational forms sometimes appear, which will cause abnormal metallographic structure, such as excessively coarse grains, uneven metal structure, and abnormal internal structure of the metal.The occurrence of the above situations is related to the on-site heat treatment process.If the steel pipe is in the heat treatment process, the improper control of the heat treatment temperature or conditions will make the metallographic phase of the metal structure abnormal. In the usual production process, the heat treatment of steel pipes is controlled according to the long-term accumulated experience. Controlling the corresponding temperature, holding time and cooling method during the heat treatment process can avoid metallographic abnormalities in the metal structure.
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